decryptSerializedStringWithKey method

@override Future<Uint8List> decryptSerializedStringWithKey(String serialized, EncryptionKey key)

Pass a string in Cryppo serialized encrypted format and a SymmetricKey (key type dependant on the scheme being used) to return binary decrypted data.

Implementation

@override
Future<Uint8List> decryptSerializedStringWithKey(
    String serialized, EncryptionKey key) {
  assert(key is SymmetricKey, 'AES requires a `SymmetricKey`');
  final items = serialized.split('.');
  final decodedPairs = items.sublist(1);

  final encryptedBytes = base64Url.decode(decodedPairs[0]);
  final encryptionArtefacts =
      EncryptionArtefacts.fromSerialized(decodedPairs[1]);

  // The `cryptography` library takes the last 16 bytes as the auth tag
  // so we need to concatenate them onto the cipher text.
  final fullCipher = Uint8List(encryptedBytes.length + _authTagLength);
  fullCipher.setAll(0, encryptedBytes);
  fullCipher.setAll(encryptedBytes.length, encryptionArtefacts.authTag);

  final mac = Mac(encryptionArtefacts.authTag);
  final secretBox =
      SecretBox(encryptedBytes, nonce: encryptionArtefacts.nonce, mac: mac);

  return _cipher
      .decrypt(
        secretBox,
        aad: encryptionArtefacts.authData,
        secretKey: SecretKey((key as SymmetricKey).bytes),
      )
      .then((value) => Uint8List.fromList(value));
}